MK and DL average about 20 million guests a year, that’s 50,000 guests a day on average, and the other parks around 10-14 million a year (25-35k) a day, even if they lost 40k a day it would mean a decrease of about 10,000 people a day at the castle parks and 5,000 a day at the other parks (roughly 20%), probably half of which would be made up because they wouldn’t have sold out days anymore and lower crowds would make for better visits and more frequent visits.
The more likely scenario is probably half that, a 10% reduction at all the parks and 5% of that loss coming back via increased visits, and the new park adding several million new visits on top of the poached guests.
Personally if I were Disney I’d happily sacrifice 2 million visits a year at MK and DL (5,000 a day per park) and 1 million visits at year at the other parks(2500 a day per park, 8 million grand total) to add another domestic park bringing in 10-20 million visits a year.
